US9358060B2

Movatterモバイル変換

Info

Publication number: US9358060B2
Application number: US13/950,419
Authority: US
Inventors: Eric P. Jerke
Original assignee: Zimmer Spine Inc
Current assignee: Highridge Medical LLC
Priority date: 2013-07-25
Filing date: 2013-07-25
Publication date: 2016-06-07
Also published as: US20160249965A1; US20150032116A1; US9931149B2

Abstract

A driver instrument for engaging and transferring rotational torque to a bone anchor already screwed into a bony structure. The driver instrument may be advanced through an incision while disengaged from the bone anchor and thereafter engaged in a driver socket of the bone anchor. The driver instrument includes an elongate shaft extending distally from a handle, a tapered distal tip, and a driver engagement feature located proximally of the tapered distal tip. The tapered distal tip and the driver engagement feature are configured such that the longitudinal rotational axis of the driver instrument automatically moves into parallel alignment with the longitudinal rotational axis of the bone anchor as the driver engagement feature of the driver instrument is advanced into the driver socket of the bone anchor.

Description

TECHNICAL FIELD

The disclosure is directed to a driver instrument for screwing a bone screw into a bony structure. More particularly, the disclosure is directed to a driver instrument configured to facilitate alignment and engagement with a bone screw as the driver instrument is advanced into the driver socket of the bone screw.

BACKGROUND

Bone anchors, such as bone screws, are commonly used in surgical procedures to attach constructs to a bony structure of a patient. For example, spinal stabilization constructs configured to stabilize a spinal segment may utilize bone screws to secure spinal rods or other elongate members to one or more vertebrae of a spinal column. The bone anchors may be screwed into the bony structure with a driver instrument.

However, in some instances it may be desirable to further screw the bone anchor into the bony structure and/or unscrew the bone anchor from the bony structure once the driver instrument has been disengaged from the bone anchor. Re-engaging the driver instrument with the bone anchor may be challenging. Accordingly, it is desirable to provide alternative driver instruments configured to engage with a bone anchor already installed in a bony structure.

SUMMARY

The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies, and uses thereof.

Accordingly, one illustrative embodiment is a method of installing a bone anchor into a bony structure. The method includes rotationally advancing a bone anchor into a bony structure to screw the bone anchor into the bony structure a first amount with a first driver instrument. The first driver instrument may then be disengaged from the bone anchor once the bone anchor has been screwed into the bony structure the first amount. Thereafter, a second driver instrument is advanced toward the bone anchor screwed into the bony structure after disengaging the first driver instrument from the bone anchor. A distal tip of the second driver instrument is advanced into a driver socket of the bone anchor screwed into the bony structure the first amount and a driver engagement feature of the second driver instrument is engaged with the driver socket of the bone anchor. The bone anchor is then further rotated (e.g., advanced and/or reversed) relative to the bony structure a second amount with the second driver instrument.

Yet another embodiment is a method of engaging a driver instrument with a bone anchor already screwed into a bony structure. The method includes advancing a driver instrument through an incision toward a bone anchor already screwed into the bony structure from a location exterior of the incision. The driver instrument is advanced through the incision while disengaged from the bone anchor. The driver instrument includes an elongate shaft extending distally from a handle, a tapered distal tip at a distal end of the elongate shaft, and a driver engagement feature located proximally of the tapered distal tip. The tapered distal tip of the driver instrument is advanced into a driver socket of the bone anchor after advancing the driver instrument through the incision and the driver engagement feature of the driver instrument is engaged with the driver socket of the bone anchor as the tapered distal tip of the driver instrument is further advanced into the driver socket of the bone anchor. The bone anchor is then rotated relative to the bony structure with the driver instrument.

The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the aspects of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the disclosure may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of an exemplary instrument for rotationally driving a bone screw;

FIG. 2 is an enlarged perspective view of the distal end region of the driver instrument ofFIG. 1;

FIG. 3 is a side view of the distal end region of the driver instrument ofFIG. 1;

FIG. 4 is an end view of the distal end region of the driver instrument ofFIG. 1; and

FIGS. 5-8 illustrate exemplary aspects of using the driver instrument ofFIG. 1 for installing a bone screw.

While the aspects of the disclosure are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may be indicative as including numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

Although some suitable dimensions, ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary.

Anexemplary driver instrument10 is illustrated atFIG. 1. Thedriver instrument10 includes ahandle12 and anelongate shaft14 extending distally from thehandle12. In some instances, thehandle12 may be removably coupled to aproximal end16 of theelongate shaft14, such as with a quick connect feature. In other instances, thehandle12 may be permanently coupled to theproximal end16 of theelongate shaft14.

Theelongate shaft14 may extend from thehandle12 to adistal end18 of theelongate shaft14. Aspects of thedistal end18 of theelongate shaft14 are further illustrated atFIG. 2. Thedistal end18 of theelongate shaft14 may include adriver engagement feature20 and adistal tip22 extending distally of thedriver engagement feature20 to a distal extremity of theelongate shaft14. As shown inFIG. 3, theelongate shaft14 may include atransition region24 proximal of thedriver engagement feature20 creating a transition from thedriver engagement feature20 to the main body portion of theelongate shaft14 extending to thehandle12.

Thedriver engagement feature20 may be of any desired configuration for mating with a complementary driver engagement feature (e.g., a driver socket) of a bone screw. For example, thedriver engagement feature20 may be an internal driver configured to be inserted in and mate with a driver socket of a bone screw. For example, thedriver engagement feature20 may include a plurality of engagement surfaces30 configured to engage a plurality of mating surfaces of the driver socket of a bone screw. In some instances thedriver engagement feature20 may be a hex driver, such as a hexalobular internal driving feature having sixengagement surfaces30 configured to engage six engagement surfaces of the driver socket of a bone screw.FIG. 4 is an end view of thedriver instrument10 showing sixengagement surfaces30 of thedriver engagement feature20 uniformly arranged in a polygonal configuration centered on the longitudinal rotational axis of theelongate shaft14 of thedriver instrument10. It is noted that other driver engagement structures, such as Torx®, may be utilized, if desired.

Referring toFIG. 3, in some instances each of the plurality of engagement surfaces30 of thedriver engagement feature20 may be arranged nonparallel to the longitudinal rotational axis X of thedriver instrument10. For example, each of the plurality of engagement surfaces30 may be positioned at an angle A from the longitudinal rotational axis X. In some instances, the angle A may be in the range of about 2 to about 8 degrees, about 2 to about 6 degrees, or about 4 to about 6 degrees from the longitudinal axis X, such as about 2 degrees, about 3 degrees, about 4 degrees, about 5 degrees, about 6 degrees, about 7 degrees, or about 8 degrees from the longitudinal rotational axis X. The tapered engagement surfaces30 of thedriver engagement feature20 may facilitate advancing thedriver engagement feature20 into a mating driver socket, for example.

Furthermore, thedistal tip22 may be a tapered distal tip extending from thedriver engagement feature20 to the distal extremity of thedriver instrument10. In some instances, the tapereddistal tip22 may be tapered at an angle B from the longitudinal rotational axis X. In some instances, the angle B may be in the range of about 25 degrees to about 75 degrees, about 30 degrees to about 60 degrees, or about 45 degrees to about 60 degrees, such as about 30 degrees, about 45 degrees or about 60 degrees.

Accordingly, the second angle B of the tapereddistal tip22 may be greater than the first angle A between the engagement surfaces30 and the longitudinal rotational axis X. Thus, thedriver engagement feature20 may be tapered toward the distal tip22 a first amount, and thedistal tip22 may be tapered toward the distal extremity of the elongate shaft14 a second amount greater than the first amount.

FIGS. 5-8 illustrate exemplary aspects of using thedriver instrument10 ofFIG. 1 for installing a bone anchor. As shown inFIG. 5, abone anchor50 may initially be installed in a bony structure100 (e.g., a vertebra, sacrum, etc.) with afirst driver instrument110. Thebone anchor50 may include a threadedbone screw52 having ahead54 and a threadedshank55 extending distally from thehead54. The threadedshaft55 may be configured to be screwed into thebony structure100. Thebone anchor50 may also include ahousing56 coupled to thebone screw52. Thehousing56 may be configured to receive and retain an elongate stabilization member (e.g., a spinal rod, a flexible member, etc.) therein for constructing a stabilization system. For example, thehousing56 may include a pair oflegs58 defining a channel therebetween to receive an elongate stabilization member therebetween. A locking member, such as a set screw, may threadably engage a threaded opening between thelegs58 to retain the elongate stabilization member in the channel.

In some instances, thehousing56 may be movably coupled to thehead54 of thebone screw52 such that thehousing56 be pivoted and/or rotated relative to thebone screw52. For example, thebone anchor50 may be a polyaxial screw in which thehousing56 may be pivoted and rotated in a plurality of orientations relative to thebone screw52. For example, thebone screw52 may have a longitudinal rotational axis Y (shown inFIG. 6) and thehousing56 may have a longitudinal axis Z (shown inFIG. 6), wherein the longitudinal axis Z of thehousing56 may be angled at a plurality of angles relative to the longitudinal rotational axis Y by pivoting thehousing56 about thehead54 of thebone screw52. Furthermore, thehousing56 may be rotated relative to thehead54 of thebone screw52 about the longitudinal axis Z.

Thefirst driver instrument110 may be any desired driver instrument adapted to rotationally advance thebone anchor50 into thebony structure100. For example, in some instances, thefirst driver instrument110 may include ashaft114 configured to engage a driver socket of thebone screw52 with the longitudinal rotational axis of theshaft114 coaxially aligned with the longitudinal rotational axis of thebone screw52. Thefirst driver instrument110 may also include asleeve112 or other structure configured to engage thehousing56 to maintain the longitudinal axis of thehousing56 in coaxial alignment with the longitudinal rotational axis of thebone screw52 as thefirst driver instrument110 screws thebone screw52 of thebone anchor50 into the bony structure100 a first amount. In some instances, thesleeve112 may be positioned external to thehousing56. In other instances, thesleeve112 may be positioned within thehousing56, such as within the threaded bore of thehousing56, or otherwise arranged in engagement with thehousing56. Accordingly, thefirst driver instrument110 may be engaged with thebone anchor50 to transfer rotational torque to thebone anchor50 in order to screw the threadedbone screw52 into thebony structure100.

Thebone anchor50 may be rotationally advanced into thebony structure100 to screw thebone anchor50 into the bony structure100 a first amount with thefirst driver instrument110. Thereafter, thefirst driver instrument110 may be disengaged from the bone anchor50 (e.g., disengaged from a driver socket of the bone screw52) once thebone anchor50 has been screwed into thebony structure100 the first amount.

In other embodiments, thedriver instrument10 may be used to pick up abone anchor50 from a surgical kit on a table of the operating room (or other location in the operating room) during a surgical procedure and transfer thebone anchor50 from exterior of a patient, through anincision120, to thebony structure100, such that thedriver instrument10 is used to screw thebone anchor50 into thebony structure100 the first amount. Accordingly, in some instances thedriver instrument10 may be the only driver instrument used to advance thebone anchor50 through theincision120 and screw thebone anchor50 into thebony structure100.

Turning toFIG. 6, if it is desired to further rotate thebone screw52 of thebone anchor50 relative to the bony structure100 (e.g., advance or screw thebone anchor50 into thebony structure100 and/or reverse or unscrew thebone anchor50 out of the bony structure100), thesecond driver instrument10 may be advanced toward thebone anchor50 screwed into thebony structure100 after disengaging thefirst driver instrument110 from thebone anchor50. It is noted that thefirst driver instrument110 may be used to screw thebone anchor50 into thebony structure100 the first amount during a surgical procedure, and thesecond driver instrument10 may be used to further screw thebone anchor50 into the bony structure100 (or otherwise rotate thebone screw52 relative to the bony structure100) a second amount during the same surgical procedure, or a subsequent surgical procedure. It is also contemplated that thedriver instrument10 may be used to initially screw thebone anchor50 into thebony structure100, thus removing the need for thefirst driver instrument110.

As shown inFIG. 6, with thebone anchor50 already screwed into thebony structure100, thedistal end18 of thedriver instrument110 may be advanced through anincision120 of the patient from a location exterior of theincision120 while disengaged from thebone anchor50. Thedistal end18 of thedriver instrument10 may be advanced distally toward thehead54 of thebone screw52. In some instances, the longitudinal rotational axis X of thedriver instrument10 may be nonparallel, and thus non-coaxial, to the longitudinal rotational 1 axis Y of thebone screw52 as thedistal end18 of theshaft14 of thedriver instrument10 is advanced toward thehead54 of thebone screw52. In some instances, the longitudinal axis Z of thehousing56 may be nonparallel, and thus non-coaxial, to the longitudinal rotational axis Y of thebone screw52 as thedistal end18 of theshaft14 of thedriver instrument10 is advanced toward thehead54 of thebone screw52. In other instances, the longitudinal rotational axis X of thedriver instrument10 may be parallel, and thus coaxial, to the longitudinal rotational 1 axis Y of thebone screw52 and/or the longitudinal rotational axis Z of thehousing56 as thedistal end18 of theshaft14 of thedriver instrument10 is advanced toward thehead54 of thebone screw52.

Turning toFIG. 7, as thedriver instrument10 is advanced distally, thedistal tip22 of thedriver instrument10 is advanced through the longitudinal bore of thehousing56 and into thedriver socket60 of thebone screw52 screwed into thebony structure100. Thedriver instrument10 need not be coaxially aligned with thebone screw52 as thedistal tip22 is advanced into thedriver socket60. Thedistal tip22 may be tapered and/or thedriver socket60 may include abeveled rim62 to facilitate advancement of thedistal tip22 into thedriver socket60.

In some instances, the longitudinal rotational axis X of thedriver instrument10 may be nonparallel, and thus non-coaxial, to the longitudinal rotational axis Y of thebone screw52 as thedistal tip22 of thedriver instrument10 is advanced into thedriver socket60 of thehead54 of thebone screw52. In some instances, the longitudinal axis Z of thehousing56 may be nonparallel, and thus non-coaxial, to the longitudinal rotational axis Y of thebone screw52 as thedistal tip22 of thedriver instrument10 is advanced into thedriver socket60 of thehead54 of thebone screw52. In other instances, the longitudinal rotational axis X of thedriver instrument10 may be parallel, and thus coaxial, to the longitudinal rotational axis Y of thebone screw52 and/or thehousing56 as thedistal tip22 of thedriver instrument10 is advanced into thehead54 of thebone screw52.

As the tapereddistal tip22 is further advanced into thedriver socket60 thedriver engagement feature20 of thedriver instrument10 may move into engagement with thedriver socket60 of thebone screw52, as shown inFIG. 8. The configuration of thedistal tip22 and thedriver engagement feature20 may allow the longitudinal rotational axis X of thedriver instrument10 to automatically move into parallel, coaxial alignment with the longitudinal axis Y of thebone screw52 as thedriver engagement feature20 of thedriver instrument10 is engaged with thedriver socket60 of thebone anchor50. For example, the angled engagement surfaces30 of the tapereddriver engagement feature20 may facilitate directing thedriver engagement feature20 into thedriver socket60 and mate the plurality of engagement surfaces30 of thedriver engagement feature20 with a plurality of mating surfaces of thedriver socket60.

Once thedriver engagement feature20 is engaged in thedriver socket60 of thebone screw52 thedriver instrument10 may be rotated to transfer rotational torque to thebone screw52 and further rotate thebone screw52 of thebone anchor50 relative to thebony structure100. For example, thedriver instrument10 may be rotated to further advance thebone screw52 of thebone anchor50 into the bony structure100 a second amount to further tighten and/or orient thebone anchor50 relative to thebony structure100. In other instances, thedriver instrument10 may be rotated to reverse or unscrew thebone screw52 of thebone anchor50 from the bony structure100 a second amount to remove and/or orient thebone anchor50 relative to thebony structure100.

Accordingly, thedriver instrument10 may facilitate engaging thehead54 of thebone screw52 to further screw thebone screw52 into the bony structure100 a second amount after afirst driver instrument110 has been disengaged from thebone screw52 after screwing thebone screw52 into the bony structure100 a first amount. In some instances, thebone screw52 may be screwed into thebony structure100 the first amount and the second amount during a single surgical procedure. In other instances, thebone screw52 may be screwed into thebony structure100 the first amount during a first surgical procedure and thebone screw52 may be screwed into thebony structure100 the second amount during a second surgical procedure, such as a revision procedure. In some instances, thedriver instrument10 may be used to unscrew thebone screw52 from thebony structure100, if desired.

It is noted that in instances in which thedriver instrument10 is engaged to thehead54 of thebone screw52 exterior of the patient, (e.g., when the driver instrument is used to pick up abone anchor50 from a surgical kit on a table of the operating room (or other location in the operating room) during a surgical procedure and transfer thebone anchor50 from exterior of a patient), similar steps as that described above may be employed. For example, thedistal end18 of thedriver instrument10 may be advanced distally toward thehead54 of thebone screw52. In some instances, the longitudinal rotational axis X of thedriver instrument10 may be nonparallel, and thus non-coaxial, to the longitudinal rotational 1 axis Y of thebone screw52 as thedistal end18 of theshaft14 of thedriver instrument10 is advanced toward thehead54 of thebone screw52. In some instances, the longitudinal axis Z of thehousing56 may be nonparallel, and thus non-coaxial, to the longitudinal rotational axis Y of thebone screw52 as thedistal end18 of theshaft14 of thedriver instrument10 is advanced toward thehead54 of thebone screw52. In other instances, the longitudinal rotational axis X of thedriver instrument10 may be parallel, and thus coaxial, to the longitudinal rotational 1 axis Y of thebone screw52 and/or the longitudinal rotational axis Z of thehousing56 as thedistal end18 of theshaft14 of thedriver instrument10 is advanced toward thehead54 of thebone screw52.

As thedriver instrument10 is advanced toward thebone screw52, thedistal tip22 of thedriver instrument10 may be advanced through the longitudinal bore of thehousing56 and into thedriver socket60 of thebone screw52. Thedriver instrument10 need not be coaxially aligned with thebone screw52 as thedistal tip22 is advanced into thedriver socket60. Thedistal tip22 may be tapered and/or thebeveled rim62 of thedriver socket60 may facilitate advancement of thedistal tip22 into thedriver socket60.

As the tapereddistal tip22 is further advanced into thedriver socket60 thedriver engagement feature20 of thedriver instrument10 may move into engagement with thedriver socket60 of thebone screw52. The configuration of thedistal tip22 and thedriver engagement feature20 may allow the longitudinal rotational axis X of thedriver instrument10 to automatically move into parallel, coaxial alignment with the longitudinal axis Y of thebone screw52 as thedriver engagement feature20 of thedriver instrument10 is engaged with thedriver socket60 of thebone anchor50. For example, the angled engagement surfaces30 of the tapereddriver engagement feature20 may facilitate directing thedriver engagement feature20 into thedriver socket60 and mate the plurality of engagement surfaces30 of thedriver engagement feature20 with a plurality of mating surfaces of thedriver socket60.

Thedriver instrument10, with thebone anchor50 engaged therewith, may then be advanced through an incision of a patient to screw thebone screw52 into a bony structure during a medical procedure. Thedriver instrument10 may be used to rotationally advance thebone anchor50 into abony structure100 to screw the bone anchor into the bony structure a first amount. Thereafter, the driver instrument may be used to rotate the bone anchor50 a second amount (e.g., further rotationally advance and/or rotationally reverse the bone screw52) relative to thebony structure100.

Those skilled in the art will recognize that aspects of the present disclosure may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departure in form and detail may be made without departing from the scope and spirit of the present disclosure as described in the appended claims.

Claims

What is claimed is:

1. A method of installing a bone anchor into a bony structure, comprising:

rotationally advancing a bone anchor into a bony structure to screw the bone anchor into the bony structure a first amount with a first driver instrument, the bone anchor comprising:

a bone screw having a longitudinal rotational axis; and

a housing pivotally coupled to a head of the bone screw, the housing having a longitudinal rotational axis that can be rotated up to a first angle from the longitudinal rotational axis of the bone screw;

wherein the bone screw is rotationally advanced by the first driver while the longitudinal rotational axis of the housing is aligned with the longitudinal rotational axis of the bone screw;

disengaging the first driver instrument from the bone anchor once the bone screw has been screwed into the bony structure the first amount;

advancing a second driver instrument toward the bone screw screwed into the bony structure after disengaging the first driver instrument from the bone anchor;

wherein the second driver instrument is advanced through the housing along the longitudinal rotational axis of the housing while the longitudinal rotational axis of the housing is offset from the longitudinal rotational axis of the bone screw;

advancing a distal tip of the second driver instrument into a driver socket of the bone screw screwed into the bony structure the first amount while the longitudinal rotational axis of the housing is offset from the longitudinal rotational axis of the bone screw;

wherein the distal tip of the second driver instrument is tapered at a second angle relative to a longitudinal rotational axis of the second driver instrument such that the distal tip is able to enter the driver socket even when the housing is displaced at the first angle;

engaging a driver engagement feature of the second driver instrument with the driver socket of the bone anchor; and

rotating the bone anchor relative to the bony structure a second amount with the second driver instrument.

2. The method ofclaim 1,

wherein the longitudinal rotational axis of the second driver instrument is nonparallel to the longitudinal rotational axis of the bone screw as the distal tip of the second driver instrument is advanced into the driver socket of the bone anchor.

3. The method ofclaim 2, wherein the longitudinal rotational axis of the second driver instrument moves into parallel alignment with the longitudinal rotational axis of the bone screw as the driver engagement feature of the second driver instrument is engaged with the driver socket of the bone anchor.

4. The method ofclaim 3,

wherein the longitudinal rotational axis of the housing is nonparallel to the longitudinal rotational axis of the bone screw as the distal tip of the second driver instrument is advanced into the driver socket of the bone anchor.

5. The method ofclaim 1, wherein an opening into the driver socket includes a beveled rim to facilitate advancement of the distal tip into the driver socket.

6. The method ofclaim 3, wherein the driver engagement feature of the second driver instrument is a hexalobular internal driving feature having six engagement surfaces configured to engage six engagement surfaces of the driver socket;

wherein the engagement surfaces of the hexalobular internal driving feature are nonparallel to the longitudinal rotational axis of the second driver instrument.

7. The method ofclaim 1, wherein the driver engagement feature of the second driver instrument includes a plurality of engagement surfaces configured to engage a plurality of mating surfaces of the driver socket;

wherein the engagement surfaces of the driver engagement feature are nonparallel to the longitudinal rotational axis of the second driver instrument.

8. The method ofclaim 7, wherein the plurality of engagement surfaces of the driver engagement feature extend at a third angle from the longitudinal rotational axis of the second driver instrument and the distal tip is tapered at the second angle from the longitudinal rotational axis of the second driver instrument, the second angle being greater than the third angle.

9. A method of installing a bone anchor into a bony structure, comprising:

screwing a threaded bone screw of a bone anchor into a bony structure a first amount with a first driver instrument using a sleeve that engages the bone anchor to ensure axial alignment between the threaded bone screw and the first driver instrument, the bone anchor including a housing pivotably coupled to a head of the threaded bone screw;

disengaging the first driver instrument from a driver socket of the head of the bone screw once the bone screw has been screwed into the bony structure the first amount, wherein the housing becomes non-coaxially aligned with the driver socket after the first driver instrument is disengaged;

advancing a second driver instrument toward the bone screw screwed into the bony structure after disengaging the first driver instrument from the driver socket of the bone screw, the second driver instrument including an elongate shaft extending distally from a handle, a tapered distal tip at a distal end of the elongate shaft, and a driver engagement feature located proximally of the tapered distal tip;

advancing the tapered distal tip of the second driver instrument into the driver socket of the bone screw screwed into the bony structure the first amount, the tapered distal tip being angled to allow the second driver to engage the driver socket when the housing is non-coaxially aligned with the driver socket;

engaging the driver engagement feature of the second driver instrument with the driver socket of the bone screw as the tapered distal tip of the second driver instrument is further advanced into the driver socket of the bone screw;

wherein a longitudinal rotational axis of the second driver instrument moves into co-axial alignment with a longitudinal rotational axis of the bone screw as the driver engagement feature of the second driver instrument is engaged with the driver socket of the bone screw; and

further screwing the threaded bone screw of the bone anchor into the bony structure a second amount with the second driver instrument.

10. The method ofclaim 9, wherein the housing of the bone anchor has a longitudinal axis aligned with the longitudinal axis of the bone screw as the threaded bone screw is screwed into the bony structure the first amount with the first driver instrument.

11. The method ofclaim 10, wherein the longitudinal axis of the housing of the bone anchor is nonparallel with the longitudinal axis of the bone screw as the tapered distal tip of the second driver instrument is advanced into the driver socket of the bone screw.

12. The method ofclaim 9, wherein the longitudinal rotational axis of the second driver instrument is nonparallel to the longitudinal rotational axis of the bone screw as the distal tip of the second driver instrument is advanced into the driver socket of the bone screw.

13. The method ofclaim 9, wherein the distal tip of the second driver instrument is tapered to facilitate advancement of the distal tip into the driver socket.

14. The method ofclaim 13, wherein an opening into the driver socket includes a beveled rim to facilitate advancement of the distal tip into the driver socket.

15. The method ofclaim 9, wherein the driver engagement feature of the second driver instrument includes a plurality of engagement surfaces configured to engage a plurality of mating surfaces of the driver socket;

16. A method of engaging a driver instrument with a bone anchor already screwed into a bony structure, comprising:

advancing a driver instrument through an incision toward a bone anchor already screwed into the bony structure from a location exterior of the incision, wherein the driver instrument is advanced through the incision while disengaged from the bone anchor, the driver instrument including:

an elongate shaft extending distally from a handle,

a tapered distal tip at a distal end of the elongate shaft, and

a driver engagement feature located proximally of the tapered distal tip, the driver engagement feature comprising a plurality of planar engagement surfaces disposed nonparallel to the longitudinal rotational axis of the second driver instrument;

advancing the tapered distal tip of the driver instrument into a driver socket of the bone anchor at a non-parallel angle after advancing the driver instrument through the incision, wherein the tapered distal tip guides the planar engagement surfaces into engagement with the driver socket;

engaging the driver engagement feature of the driver instrument with the driver socket of the bone anchor as the tapered distal tip of the driver instrument is further advanced into the driver socket of the bone anchor, wherein the planar engagement surfaces facilitate parallel alignment of the driver instrument and the bone anchor; and

rotating the bone anchor relative to the bony structure with the driver instrument.

17. The method ofclaim 1, wherein the bone screw is rotationally advanced by the first driver using a sleeve that maintains the longitudinal axis of the housing aligned with the longitudinal axis of the bone screw.

18. The method ofclaim 1, wherein the second angle is less than the first angle.